JP6022466B2 - Emulsion-like reaction mixture and process for producing polyurethane foam from such reaction mixture - Google Patents

Description

  The present invention relates to an emulsion-like reaction mixture suitable for conversion to polyurethane comprising a first phase and a second phase in an emulsion, which comprises a polyol, a blowing agent, a surfactant and an isocyanate. . The invention also relates to a process for the production of polyurethane foam by feeding such a reaction mixture, the use of such a reaction mixture for producing a polyurethane foam and the resulting polyurethane foam.

One purpose of industrial research and development is to produce nanocellular foams. One field of application of nanocellular foams is, for example, thermal insulation of buildings, tubes and cooling devices. For this, the advantage of the Knudsen effect can be exploited. If the internal structure of the foam is within the range of the mean free path of gas molecules, the thermal conductivity is significantly reduced. For heat insulation, it is preferable that the foam can be produced in a large block shape. Conventional plastic foams typically contain 10 ³ to 10 ⁶ cells per cm ³ . It is desirable that the bubble density be higher than 10 ⁹ cm ⁻³ .

  Polymer foams are manufactured using various foaming agents. A foaming agent is used to foam the polymer, polymerization liquid or polymerizable mixture. The blowing agent may be gaseous or may be a highly volatile component that evaporates with heat or heat of polymerization reaction.

  Subsequently, the system becomes supersaturated and bubbles are likely to be generated. In this state, the system is not thermodynamically balanced, and to do so requires a bubble nucleation process. For both homogeneous and heterogeneous nucleation, this process involves an energy barrier that must be overcome to form individual bubbles. The resulting foam is macrocellular.

  In general, little is known about the details of the nucleation process in technical applications and it is difficult to control. Changes can result in a fairly diverse product of foam homogeneity and properties. Although particle addition or bubble introduction is performed in an attempt to initiate nucleation, the number density of bubbles cannot be significantly increased with this method. In addition, non-uniform particles remain in the final product.

  Microemulsions can be one way to avoid the need for very high pressures. Microemulsions result from the use of surfactants to convert water and oils into macroscopically uniform and thermodynamically stable nanometer structure dispersions. By appropriately selecting the composition, pressure and temperature, a great variety of structures can be formed. For example, oil-in-water (O / W) microemulsions contain oils as nanometer sized oily droplets with a surfactant film as the outer film. Oils, typically condensed hydrocarbons, can be replaced by short chain hydrocarbons such as ethane or propane, or carbon dioxide. In particular, water-in-oil or water-in-carbon dioxide microemulsions having the opposite structure have been described in more recent technical literature. In these types of microemulsions, the aqueous component is the internal phase and the supercritical fluid is the external phase. More recently, microemulsions of non-aqueous polar components, homopolymers and amphiphilic block copolymer microemulsions have also been reported.

  In the POSME method (Principle of Supercritical Microemulsion Expansion), the blowing agent is present as very small droplets in the polar phase of the microemulsion. The diameter of such droplets can range from 1 to 100 nm.

The POSME method is described in DE 102 60 815 A1. This document discloses a foam material and a method for producing the foam material. It has been described that nano-sized bubble-containing foam materials can be produced without the need to overcome the energy barrier normally present in phase transition and nucleation processes. A related object is to control and produce foam materials with a cell number density of 10 ¹² to 10 ¹⁸ cm ⁻³ and an average cell diameter of 10 nm to 10 μm. The main component for this is a dispersion in the first fluid matrix of the pool-like second fluid. In the reaction space, the first fluid exists as a matrix and the second fluid exists in the pool. By adjusting the pressure and / or temperature, the second fluid is brought into a near critical or supercritical state having a density close to that of a liquid. The second fluid is present completely or almost completely in a pool and is uniformly distributed throughout the first fluid. Upon release, the second fluid returns to a gas-like density and the pool expands to produce nanometer sized bubbles. There is no need to cross the energy barrier and the blowing agent molecules need not diffuse into the growing bubbles.

  Although it is described that a polymerizable substance is generally useful as the first fluid, only acrylamide that is polymerized to polyacrylamide and melamine that is polymerized to melamine resin are described. The second fluid must be selected from the group consisting of hydrocarbons such as methane or ethane, alkanols, (hydro) chlorofluorocarbons and carbon dioxide. In addition, an amphiphile is used, which must have at least one block that is compatible with the first fluid and at least one block that is compatible with the second fluid.

  Thus, in this patent document, the reaction components required to form the polymer are present in the same phase of the emulsion.

  Another example of a polymerizable reaction mixture in a supercritical solvent is disclosed in US 5,387,619. This document relates to a method for inhibiting chemical reactions in fluid reactive organic materials by mixing with supercritical or near-critical fluids, in particular supercritical carbon dioxide. This method includes the possibility of using a supercritical fluid (preferably carbon dioxide) to suppress chemical reactions that normally occur between functionally compatible organic molecules. This reaction can occur at a predetermined but unusual time. In particular, a system comprising polyol, carbon dioxide, catalyst and MDI is described. After reducing the pressure to subcritical conditions, a polyaddition reaction occurs, which has been observed by a sudden increase in the viscosity of the mixture.

  Polyurethane foams can be produced by dissolving supercritical carbon dioxide in the TDI component and thus serving as a foaming agent in foam formation, as described in EP 0 353 061 A2. However, nothing has been reported about microcellular foams or nanocellular foams.

  Another method for producing the polymer is interfacial polymerization. The two reactants to produce the polymer are reacted at the interface between the phases. One well-known example is the production of nylon-6,10 in which hexamethylenediamine and sebacoyl chloride in a suitable solvent for each are reacted through a macroscopic interface that are not miscible with each other.

  An example of producing a foam using chemical components in both phases is disclosed in WO 2004/050752 A1. The document relates to compositions and methods for producing high internal emulsion (HIPE) foams and inverse high internal emulsion (I-HIPE) foams by using supercritical fluids. This type of foam is particularly useful for absorbent articles. The method includes mixing an aqueous phase comprising an effective amount of at least one superabsorbent precursor monomer and a supercritical fluid phase. Mix an oxidation initiator in one of the supercritical phases or the aqueous phase with a reduction initiator in another supercritical and aqueous phase. The supercritical phase and the aqueous phase form an emulsion in which polymerization of at least one superabsorbent precursor monomer occurs. Generally, redox polymerization occurs following the mixing of the oxidation initiator and the reduction initiator, but not at the phase boundary between the aqueous phase and the supercritical fluid phase.

DE 102 60 815 A1 US 5,387,619 EP 0 353 061 A2 WO 2004/050752 A1

  From the above, it is clear that there is a continuing need for alternative methods for producing polyurethane foams having smaller cell sizes and reaction mixtures used in the methods.

This purpose comprises a first phase and a second phase in the emulsion, in which the following ingredients are:
A) Polyol, polyether polyol, polyester polyol, polycarbonate polyol, polyether ester having a hydroxyl number of 100 mg KOH / g to 800 mg KOH / g, preferably 350 mg KOH / g to 650 mg KOH / g and an average hydroxyl functionality of 2 or more An isocyanate-reactive compound selected from the group consisting of polyols and polyacrylate polyols;
B) a linear, branched or cyclic _C 1 -C ₅ alkanes, linear, blowing agent selected from branched or cyclic _C 1 -C ₅ fluoroalkanes and the group consisting of carbon dioxide,
C) alkoxylated alkanol, alkoxylated alkylphenol, alkoxylated fatty acid, fatty acid ester, polyalkyleneamine, alkyl sulfate, alkyl polyether, alkyl polyglucoside, phosphatidylinositol, fluorinated surfactant, siloxane group-containing surfactant and bis A surfactant selected from the group consisting of (2-ethyl-1-hexyl) sulfosuccinate;
D) An emulsion-like reaction mixture suitable for conversion to polyurethane comprising an isocyanate having an isocyanate functionality of 2 or more,
It has been found that this is achieved according to the invention with a reaction mixture in which the isocyanate-reactive compound A) is present in the first phase of the emulsion and the blowing agent B) is present in the second phase.

FIG. 1 shows an emulsion of a near-critical or supercritical blowing agent containing a reactant in an outer phase containing another reactant. FIG. 2 shows the state of the emulsion of FIG. 1 after a pressure drop. FIG. 3 shows an enlarged view of the phase boundary when the reactants are reacting. FIG. 4 is an electron micrograph of the polyurethane foam obtained in Example 1 of the present invention. FIG. 5 is an optical micrograph of the polyurethane foam obtained in Example 2 of the present invention. FIG. 6 is an optical micrograph of the polyurethane foam obtained in Example 3 of the present invention. FIG. 7 is an optical micrograph of the polyurethane foam obtained in Example 4 of the present invention. FIG. 8 is an optical micrograph of the polyurethane foam obtained in Comparative Example 5.

The composition of the present invention comprises:
The blowing agent B) is present in a near-critical or supercritical state,
Isocyanate D) is present in the second phase in a proportion of not less than 10% by weight, based on the total amount of isocyanate D) in the composition.

を満たす温度Ｔが存在することを意味すると理解される。この条件は、

または

であってもよい。 Accordingly, the reaction mixture of the present invention comprises two adjacent phases that are at least partially immiscible with each other, the first phase comprises a polyol and the second phase comprises a blowing agent and an isocyanate. It is preferred that the second phase exists as an internal phase, i.e., for example, as a droplet in the first phase. The blowing agent exists in a supercritical state. This condition is that above the critical temperature T _c and the critical pressure p _c. However, the blowing agent may be present in a near critical state. This is based on the condition that the critical temperature T _c of the blowing agent is:

It is understood to mean that there exists a temperature T that satisfies This condition is

Or

It may be.

  The blowing agent may be present, for example, with a droplet size of 1 nm to 100 nm. The droplet size may be between 3 nm and 30 nm. Droplet size can be measured, for example, by dynamic light scattering or small angle neutron scattering and is understood as the average droplet size. This type of droplet size is achieved in particular when the reaction mixture according to the invention is in the form of a microemulsion. Small droplet sizes are advantageous because further processing of the composition into polymer foam results in small cell sizes in the resulting foam.

  Moreover, isocyanate exists in a 2nd phase in the ratio of 10 weight% or more with respect to the total amount of the isocyanate in a composition. This proportion may be higher, for example 80% or more or 90% or more. The isocyanate may be dissolved, suspended, emulsified or otherwise present in the blowing agent phase.

  After producing the reaction mixture, the emulsifying foaming agent may be subcritical conditions to convert it to the gas phase, thereby forming a microcellular foam or nanocellular foam. At the same time, the isocyanate becomes available for interfacial polymerization with the polyol, which cures the cell walls of the foam. Without being bound by a particular theory, it is believed that the amount of surfactant is no longer sufficient to separate the polyol and isocyanate from each other. In the present invention, interfacial polymerization is understood to mean an interfacial polyaddition reaction between a polyol and an isocyanate.

Polyols that can be used according to the present invention may have a number average molecular weight M _n of, for example, 62 g / mol to 8000 g / mol, preferably 90 g / mol to 5000 g / mol, more preferably 92 g / mol to 1000 g / mol. When a single polyol is added, the hydroxyl number is that of the polyol. When adding the mixture, the average hydroxyl number is employed. This value may be measured according to DIN 53240. The average hydroxyl functionality of the polyol is 2 or more, for example 2-6, preferably 2.1-5, more preferably 2.2-4.

  An example of a polyether polyol that can be used according to the invention is a polytetramethylene glycol polyether obtainable by polymerization of tetrahydrofuran by cationic ring opening.

  Another useful polyether polyol includes the addition product of styrene oxide, ethylene oxide, propylene oxide, butylene oxide and / or epichlorohydrin to a difunctional or polyfunctional starter molecule.

  Examples of suitable starter molecules are water, ethylene glycol, diethylene glycol, butyl diglycol, glycerol, diethylene glycol, trimethylolpropane, propylene glycol, pentaerythritol, sorbitol, sucrose, ethylenediamine, toluenediamine, triethanolamine, 1,4- Butanediol, 1,6-hexanediol, and low molecular weight hydroxyl-containing esters of this type of polyol and dicarboxylic acid.

  Polyester polyols that can be used according to the invention include polycondensates of diols and further triols and tetraols with dicarboxylic acids and further tricarboxylic acids and further tetracarboxylic acids or hydroxycarboxylic acids or lactones. Instead of the free polycarboxylic acids, the corresponding polycarboxylic anhydrides or the corresponding polycarboxylic esters of lower alcohols can also be used for the preparation of the polyesters.

  Examples of suitable diols are ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycol, as well as 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol and isomers thereof, neopentyl glycol, or hydroxypivalic acid neopentyl glycol ester. In addition to these, other polyols that can be used are polyols such as trimethylolpropane, glycerol, erythritol, pentaerythritol, trimethylolbenzene or trishydroxyethyl isocyanurate.

  Examples of polycarboxylic acids that can be used are phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, tetrachlorophthalic acid, maleic acid , Fumaric acid, itaconic acid, malonic acid, suberic acid, succinic acid, 2-methylsuccinic acid, 3,3-diethylglutaric acid, 2,2-dimethylsuccinic acid, dodecanedioic acid, endomethylenetetrahydrophthalic acid, dimer fatty acid, Trimer fatty acid, citric acid or trimellitic acid. The corresponding anhydride can also be used as a source of acid.

  If the average functionality of the polyol to be esterified is 2 or more, monocarboxylic acids such as benzoic acid and hexanecarboxylic acid can also be used.

  Examples of hydroxycarboxylic acids that may be used as additional reactants in the preparation of terminal hydroxyl group-containing polyester polyols are hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid, hydroxystearic acid and the like. Suitable lactones include caprolactone, butyrolactone and homologues.

  Polycarbonate polyols that can be used according to the present invention are hydroxyl-containing polycarbonates such as polycarbonate diols. They can be obtained by reaction of carboxylic acid derivatives (eg diphenyl carbonate, dimethyl carbonate or phosgene) with polyols (preferably diols) or by reaction of epoxides (eg propylene oxide) with carbon dioxide.

  Examples of this type of diol are ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,8- Octanediol, neopentyl glycol, 1,4-bishydroxymethylcyclohexane, 2-methyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, dipropylene glycol, polypropylene glycol, di Butylene glycol, polybutylene glycol, bisphenol A, and lactone-modified diols of the above compounds.

  Polyether-polycarbonate diols can also be used instead of or in addition to pure polycarbonate diols.

  Polyether ester polyols that can be used in accordance with the present invention are compounds containing ether groups, ester groups and hydroxyl groups. Suitable compounds for the preparation of polyetherester polyols are organic dicarboxylic acids having up to 12 carbon atoms, preferably aliphatic dicarboxylic acids having 4 to 6 carbon atoms, or aromatic dicarboxylic acids, Are used alone or as a mixture. Examples which may be mentioned are suberic acid, azelaic acid, decanedicarboxylic acid, maleic acid, malonic acid, phthalic acid, pimelic acid and sebacic acid, in particular glutaric acid, fumaric acid, succinic acid, adipic acid, phthalic acid, terephthalic acid and Isoterephthalic acid. Examples of derivatives of these acids that can be used are their anhydrides and their esters and semiesters with low molecular weight monohydric alcohols having 1 to 4 carbon atoms.

  Another component used to prepare the polyetherester polyol is a polyether polyol obtained by alkoxylation of a starter molecule such as a polyhydric alcohol. The starter molecule is at least difunctional but may optionally contain higher functionality starter molecules, especially trifunctional starter molecules.

Examples of starter molecules are diols having primary hydroxyl groups and having a number average molecular weight M _n of 18 g / mol to 400 g / mol or 62 g / mol to 200 g / mol, such as 1,2-ethanediol, 1 , 3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,10-decane Diol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propane Diol, 2-butene-1,4-diol, 2-butyne-1,4-diol, ether diol, such as diethylene glycol , Triethylene glycol, tetraethylene glycol, dibutylene glycol, tributylene glycol, tetrabutylene glycol, dihexylene glycol, trihexylene glycol, tetrahexylene glycol, and an oligomeric mixture of alkylene glycols (eg, diethylene glycol).

  In addition to diols, polyols having a number average functionality of 2-8 or 3-4 may further be used, examples being 1,1,1-trimethylolpropane, triethanolamine, glycerol, sorbitan and Pentaerythritol and preferably a polyethylene oxide polyol having an average molecular weight of 18 g / mol to 400 g / mol or 62 g / mol to 200 g / mol and starting from triols or tetraols.

  Polyacrylate polyols can be obtained by radical polymerization of hydroxyl-containing olefinically unsaturated monomers or by radical copolymerization of hydroxyl-containing olefinically unsaturated monomers, which may optionally be accompanied by another olefinically unsaturated monomer. Examples of other olefinically unsaturated monomers are ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isobornyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, styrene, acrylic acid, acrylonitrile And / or methacrylonitrile. Suitable hydroxyl-containing olefinically unsaturated monomers are in particular 2-hydroxylethyl acrylate, 2-hydroxyethyl methacrylate, a hydroxypropyl acrylate isomer mixture obtainable by addition of propylene oxide to acrylic acid, and propylene to methacrylic acid Hydroxypropyl methacrylate isomer mixture which can be obtained by addition of oxides. The terminal hydroxyl group may be present in a protected state. Suitable radical initiators are initiators selected from the group of azo compounds, such as azoisobutyronitrile (AIBN), or initiators selected from the group of peroxides, such as di-tert-butyl peroxide.

The blowing agent B) that can be used in the present invention may be used in a near-critical or supercritical state. For example, supercritical carbon dioxide may be used. Carbon dioxide may be introduced from the outside or may be generated by reaction of water with isocyanate groups. Examples of other blowing agents are linear C ₁ -C ₅ alkanes, branched C ₄ -C ₅ alkanes and cyclic C ₃ -C ₅ alkanes. Specific examples of blowing agents are methane, ethane, propane, n-butane, isobutane, n-pentane and / or cyclopentane. Another example is a partially fluorinated or perfluorinated derivative of methane, ethane, propane, n-butane, isobutane, n-pentane and / or cyclopentane.

  Examples of alkoxylated alkanols that can be used as surfactant component C) according to the invention are linear or branched alkanols having 6 to 30 carbon atoms and polyalkylene glycols having 2 to 100 alkylene oxide units. Ether. They may be, for example, ethers of linear alkanols having 15 to 20 carbon atoms and polyalkylene glycols having 5 to 30 ethylene oxide units.

  Also, alkoxylated alkylphenols, alkoxylated fatty acids, fatty acid esters, polyalkyleneamines, alkyl sulfates, alkyl polyethers, alkylpolyglucosides, phosphatidylinositols, fluorinated surfactants, polysiloxane group-containing surfactants and / or bis ( 2-Ethyl-1-hexyl) sulfosuccinate can also be used.

  The fluorinated surfactant may be a perfluorinated surfactant or a partially fluorinated surfactant. Examples are partially fluorinated ethoxylated alkanols or carboxylic acids such as perfluorooctanoic acid.

  An example of a polysiloxane group-containing surfactant may be a siloxane-terminated polyalkylene oxide polyether. These surfactants may have a linear or branched structure. This type of surfactant used according to the invention can be obtained, for example, by hydrosilylation of unsaturated compounds with Si-H group-containing polysiloxanes. The unsaturated compound may in particular be a reaction product of allyl alcohol and ethylene oxide or propylene oxide.

The surfactant can also be obtained, for example, by reaction between polyether alcohol and Si—Cl group-containing polysiloxane. In the polyether, all end groups may be siloxane ends. Mixed end groups can also be present, and siloxane end groups and hydroxy end groups or reaction functionalized hydroxy end groups such as methoxy groups can be present. The siloxane end is a monosiloxane group R ₃ Si—O— or an oligo or polysiloxane group R ₃ Si—O— [R ₂ Si—O] _n — [AO], for example, where n is 1 to 100, Good. In the case of branched surfactants, the siloxane ends are for example according to R ₃ Si—O—RSi [AO] —O— [R ₂ Si—O] _m —O—SiR ₃ , where m is 0 to 10 or m + n. May be configured as a comb polymer according to R ₃ Si—O— [RSi [AO]] _n —O— [R ₂ Si—O] _m —O—SiR _{3 wherein} In these cases, the R group is preferably an alkyl group, in particular a methyl group. The group [AO] is a polyalkylene oxide group, preferably polyethylene oxide and / or polypropylene oxide. The group [AO] may be bonded to the siloxane via a linking group, for example C ₃ H ₆ .

  The composition according to the invention further contains as component D) an isocyanate having an isocyanate functionality of 2 or more. This type of isocyanate is also referred to as polyisocyanate. Accordingly, when the reaction mixture is reacted, a polyurethane foam or a polyisocyanurate foam is obtained.

Examples of suitable polyisocyanates of this type are 1,4-butylene diisocyanate, 1,5-pentane diisocyanate, 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 2,2,4-trimethylhexa Methylene diisocyanate and / or 2,4,4-trimethylhexamethylene diisocyanate, isomeric bis (4,4′-isocyanatocyclohexyl) methane or mixtures having any isomer content thereof, 1,4-cyclohexylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate (TDI) and / or 2,6-tolylene diisocyanate, 1,5-naphthylene diisocyanate, 2,2′-diphenylmethane diisocyanate (MDI) and / or 2,4′-diphenylmethane diisocyanate and / or 4,4′-diphenylmethane diisocyanate or higher homologues (polymer MDI), 1,3-bis (2-isocyanatoprop-2-yl) benzene (TMXDI) and / or 1,4-bis (2-isocyanatoprop-2-yl) benzene, 1,3-bis (isocyanatomethyl) benzene _(XDI), alkyl having C 1 -C ₆ alkyl group - 2,6-diisocyanatohexanoate (lysine diisocyanate).

  Modifications having a uretdione structure, isocyanurate structure, urethane structure, carbodiimide structure, uretonimine structure, allophanate structure, biuret structure, amide structure, iminooxadiazinedione structure and / or oxadiazinetrione structure in addition to the above polyisocyanates Diisocyanates, as well as unmodified polyisocyanates having 3 or more isocyanate groups per molecule, such as 4-isocyanatomethyl-1,8-octane diisocyanate (nonane triisocyanate) or triphenylmethane-4,4 ′, 4 ′ '-Triisocyanate can also be used.

  In the reaction mixture, the number of isocyanate groups in the isocyanate and the number of isocyanate-reactive groups in component A) may be a ratio of 70: 100 to 500: 100. This index may be in the range of 180: 100 to 330: 100 or 90: 100 to 140: 100.

The proportion of components A), B), C) and D) present in the reaction mixture according to the invention can be, for example,
Component A): 5% to 70% by weight, preferably 10% to 60% by weight, more preferably 20% to 50% by weight;
Component B): 1% to 30% by weight, preferably 2% to 20% by weight, more preferably 3% to 15% by weight;
Component C): 1 wt% to 50 wt%, preferably 3 wt% to 30 wt%, more preferably 5 wt% to 25 wt%; and Component D): 5 wt% to 80 wt%, preferably 20 wt% % To 70% by weight, more preferably 30% to 60% by weight.

  Embodiments of the present invention are described below. These aspects may be freely combined with each other unless clearly contradicted.

  In one embodiment of the reaction mixture of the present invention, isocyanate D) comprises diphenylmethane-4,4'-diisocyanate and tolylene diisocyanate.

  Surprisingly, the combination of diphenylmethane diisocyanate-based isocyanates (2,2′- and / or 2,4′- and / or 4,4′-MDI or polymeric MDI) with at least carbon dioxide soluble isocyanates It has been found that extremely fine foams are produced.

  In the present invention, diphenylmethane diisocyanate-based isocyanate is preferably combined with TDI (preferably 2,4-TDI and / or 2,6-TDI).

  In another embodiment of the reaction mixture of the present invention, isocyanate D) is present in the second phase in a proportion of 90% to 100% by weight relative to the total amount of isocyanate D) in the composition. That is, the isocyanate is preferably present completely or substantially completely in the blowing agent phase. The proportion of isocyanate may range from 95% to 100% by weight or from 98% to 100% by weight. Increasing the proportion of isocyanate dissolved in the blowing agent phase and correspondingly decreasing the proportion of isocyanate dissolved in the polyol phase increases the effectiveness with which polymerization can proceed at the phase interface.

  Advantageously, in the reaction mixture according to the invention, the isocyanate D) is dissolved in the blowing agent B). In the present invention, mixtures of different isocyanates are also included.

  In another aspect of the reaction mixture of the present invention, the reaction mixture is present at a pressure of 30 bar to 300 bar and a temperature of 0 ° C to 100 ° C. The pressure may be in the range of 40 bar to 150 bar or 60 bar to 100 bar. The temperature may be in the range of 10 ° C to 80 ° C or 20 ° C to 60 ° C.

  In another embodiment of the reaction mixture of the present invention, the isocyanate-reactive component A) comprises a bifunctional polyester polyol having a hydroxyl number of 240 mg KOH / g to 340 mg KOH / g.

In another embodiment of the method of the present invention, surfactant B) is an oligodimethylsiloxane end group-containing polyethylene oxide polyether having 5 or less dimethylsiloxane units. An example of this type of polyether is the ideal formula: R′O— [CH ₂ CH ₂ O] _o —X—SiR (O—SiR ₃ ) ((O—SiR ₂ ) _p R), where R═CH ₃ , R ′ = H, CH ₃ or COCH ₃ ]. Where X may be any linking group, such as alkyl-α or ω-diyl, o is 1-100, preferably 5-30, more preferably 10-20 and p is 2 or less. is there. The group X may be, for example, —CH ₂ —CH ₂ —CH ₂ —. A preferred surfactant is 3- (polyoxyethylene) propylheptamethyltrisiloxane. This is commercially available from Dow Corning under the trade name Q2-5211®.

In another embodiment of the reaction mixture of the present invention, the components are in the following proportions:
20% to 45% by weight of a mixture of a difunctional polyester polyol having a hydroxyl number of 290 mg KOH / g to 320 mg KOH / g and glycerol,
Carbon dioxide 4 wt% to 20 wt%,
5% to 25% by weight of siloxane-polyalkylene oxide copolymer, and diphenylmethane-4,4'-diisocyanate and its isomers and higher functional homologues, 2,4-tolylene diisocyanate and 2,6- Mixture with tolylene diisocyanate 20% to 40% by weight
The total of the weight ratios of the individual components is 100% by weight or less.

The present invention also provides
Providing an isocyanate-reactive compound A), a blowing agent B) present in a near-critical or supercritical state, a surfactant C) and an isocyanate D) having the meaning according to the previous definition, and A method for producing a polyurethane foam comprising the step of reducing the pressure of the composition to convert the foaming agent into a gaseous state is provided.

  The isocyanate is at least partially present in the blowing agent phase. It is preferable that it exists in the state melt | dissolved in it. The isocyanate in the blowing agent phase does not react with the polyol as long as the conditions are near or supercritical. As the blowing agent expands, the isocyanate and polyol come into direct contact and interfacial polymerization can occur.

This method is preferably
Supplying a composition according to the invention comprising an isocyanate-reactive compound A), a blowing agent B) present in a near-critical or supercritical state, and a surfactant C);
Adding the isocyanate D) according to the invention, whereby the isocyanate D) migrates into the blowing agent B) and reducing the pressure of the resulting composition mixture to bring the blowing agent into the gaseous state Including the step of conversion.

  In this variant, first an emulsion or microemulsion comprising a polyol phase and a blowing agent phase is prepared. The subsequently added isocyanate is at least partially present in the blowing agent phase. It is preferable that it exists in the state melt | dissolved in it. The isocyanate in the blowing agent phase does not react with the polyol as long as the conditions are near or supercritical. As the blowing agent expands, the isocyanate and polyol come into direct contact and interfacial polymerization can occur.

  In one embodiment of this method, the blowing agent-containing composition is maintained at a pressure of 1 bar to 300 bar and a temperature of 0 ° C to 100 ° C. The pressure may be in the range of 10 bar to 180 bar or 20 bar to 150 bar. The temperature may range from 10 ° C to 80 ° C or from 20 ° C to 60 ° C.

  In another aspect of this method, the blowing agent component B) is converted to a subcritical state in a closed mold, which is not part of the mixing head of the mixing device, and its internal volume and / or after introduction of the mixture. It is designed so that its internal pressure can be changed by external action.

The present invention further includes
Supplying a composition comprising an isocyanate-reactive compound A) and a surfactant C) according to the invention,
Supplying a composition according to the invention comprising a blowing agent component B) present in a near-critical or supercritical state and an isocyanate D) present in the blowing agent B);
-Mixing the two compositions;
-The manufacturing method of a polyurethane foam including the process of reducing the pressure of the obtained composition mixture and converting a foaming agent into a gaseous state is provided.

  In this variant, the isocyanate is already present in the near-critical or supercritical blowing agent before mixing with the polyol phase. It is preferable that the isocyanate exists in a state dissolved in the foaming agent. More preferably, the composition obtained by mixing the polyol phase and the blowing agent phase is further maintained under conditions where the blowing agent is in a near-critical or supercritical state.

  In one embodiment of this method, the blowing agent-containing composition is maintained at a pressure of 1 bar to 300 bar and a temperature of 0 ° C to 100 ° C. The pressure may be in the range of 10 bar to 180 bar or 20 bar to 150 bar. The temperature may range from 10 ° C to 80 ° C or from 20 ° C to 60 ° C.

  The invention further relates to a polyurethane foam obtained by the method described above.

The polyurethane foam of the present invention may be a foam having an average pore diameter of, for example, 10 nm to 10,000 nm. Regardless, the pore density of the polyurethane foam of the present invention may be 10 ⁷ pores / cm ³ to 10 ¹⁸ pores / cm ³ .

  The present invention also provides the use of the reaction mixture of the present invention to produce a polyurethane foam.

The method of the present invention will be schematically described with reference to FIGS.
FIG. 1 shows an emulsion of a near-critical or supercritical blowing agent containing a reactant in an outer phase containing another reactant.
FIG. 2 shows the state of the emulsion of FIG. 1 after a pressure drop.
FIG. 3 shows an enlarged view of the phase boundary when the reactants are reacting.
4 to 8 are photomicrographs of polyurethane foam.

  FIG. 1 shows an emulsion in an outer phase containing another dissolved reactant of a near-critical or supercritical blowing agent containing the dissolved reactant. This emulsion, which may be a microemulsion, comprises an outer phase 1 and a droplet-like inner phase 2. The reactant in the polar outer phase 1 is the schematically depicted polyol 3. This outer phase 1 is solvent-free or comprises water, polar solvents, volatile solvents and mixtures thereof as additional solvents. In addition to the polyol 3, the outer phase 1 may additionally contain polymers and additives such as water, flame retardants such as TCPP, or salts.

  The nonpolar internal phase 2 contains a near-critical or supercritical blowing agent, such as carbon dioxide, methane, ethane, propane or mixtures thereof. The internal phase 2 further contains an isocyanate 4 having an isocyanate functionality of 2, which is schematically depicted. Isocyanate 4 is present in the internal phase 2, and thus in the blowing agent, dissolved, suspended, emulsified or otherwise. The inner phase 2 and the outer phase 1 are separated by surfactant molecules 5 with the hydrophilic head facing the outer phase 1 and the lipophilic tail facing the inner phase 2.

  FIG. 2 shows the state of the emulsion of FIG. 1 after the pressure drop, ie after the near-critical or supercritical fluid in the internal phase 2 has been converted to a gaseous state. In the method of the present invention, the fluid droplet expands. As a result, the amount of surfactant molecules 5 is no longer sufficient to separate the inner phase 2 and the outer phase 1. Thus, the two phases come into direct contact. This is drawn as the phase boundary 6. At this time, since the fluid in the internal phase 2 is in a gaseous state, the dissolving ability, suspending ability, emulsifying ability or other adaptability of the isocyanate 4 is lowered. Therefore, in the case of a solution, the isocyanate 4 precipitates. The precipitated isocyanate 4 at the phase boundary 6 is not separated from the polar phase by the surfactant molecules 5 and comes into direct contact with the polyol 3. As a result, these reactants react with each other.

  FIG. 3 shows an enlarged view of the phase boundary when the reactants are reacting. As the bubbles in the inner phase 2 continue to expand, they come into contact and the isocyanate molecules at the edge of one bubble in the inner phase 2 can react with the polyol molecules 3 in the outer phase 1 and free functional groups of the polyol molecules 3 Can further react with isocyanate 4 in another cell. In this way, the cell walls of the obtained foam are stabilized and a foam is obtained.

The following examples illustrate the invention.
Preferred embodiments of the present invention include the following.
[1] The emulsion comprises a first phase and a second phase, and the following components are contained therein:
A) Selected from the group consisting of polyols, polyether polyols, polyester polyols, polycarbonate polyols, polyether ester polyols and polyacrylate polyols having a hydroxyl number of 100 mg KOH / g to 800 mg KOH / g and an average hydroxyl functionality of 2 or more. Isocyanate-reactive compounds,
B) a linear, branched or cyclic _C 1 -C ₅ alkanes, linear, blowing agent selected from branched or cyclic _C 1 -C ₅ fluoroalkanes and the group consisting of carbon dioxide,
C) alkoxylated alkanol, alkoxylated alkylphenol, alkoxylated fatty acid, fatty acid ester, polyalkyleneamine, alkyl sulfate, alkyl polyether, alkyl polyglucoside, phosphatidylinositol, fluorinated surfactant, siloxane group-containing surfactant and bis A surfactant selected from the group consisting of (2-ethyl-1-hexyl) sulfosuccinate;
D) Isocyanates having an isocyanate functionality of 2 or more
An emulsion-like reaction mixture suitable for conversion to polyurethane comprising
Isocyanate-reactive compound A) is present in the first phase of the emulsion and blowing agent B) is present in the second phase;
The blowing agent B) is present in a near-critical or supercritical state,
Reaction mixture, characterized in that isocyanate D) is present in the second phase in a proportion of not less than 10% by weight, based on the total amount of isocyanate D) in the composition.
[2] The reaction mixture according to the above [1], wherein the isocyanate D) comprises diphenylmethane-4,4′-diisocyanate and tolylene diisocyanate.
[3] The reaction mixture according to the above [1], wherein the isocyanate D) is dissolved in the foaming agent B).
[4] The reaction mixture according to [1], which exists at a pressure of 30 bar to 300 bar and a temperature of 0 ° C. to 100 ° C.
[5] The reaction mixture according to the above [1], wherein the isocyanate-reactive component A) comprises a bifunctional polyester polyol having a hydroxyl number of 240 mgKOH / g to 340 mgKOH / g.
[6] The reaction mixture according to the above [1], wherein the surfactant component B) is an oligodimethylsiloxane end group-containing polyethylene oxide polyether having 5 or less dimethylsiloxane units.
[7] Component is the following ratio:
20% to 45% by weight of a mixture of a difunctional polyester polyol having a hydroxyl number of 290 mg KOH / g to 320 mg KOH / g and glycerol,
Carbon dioxide 4 wt% to 20 wt%,
5% to 25% by weight of siloxane-polyalkylene oxide copolymer, and
A mixture of diphenylmethane-4,4′-diisocyanate and their isomers and high functional homologues with 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate 20% to 40% by weight
The reaction mixture according to [1] above, wherein the total weight ratio of the individual components is 100% by weight or less.
[8] A step of supplying an isocyanate-reactive compound A) having a meaning described in [1] above, a foaming agent B) existing in a near-critical or supercritical state, a surfactant C) and an isocyanate D). and
-A step of reducing the pressure of the obtained composition to convert the foaming agent into a gaseous state.
A process for producing a polyurethane foam, comprising:
[9] The method according to [8] above, wherein the composition comprising the blowing agent is maintained at a pressure of 1 bar to 300 bar and a temperature of 0 ° C to 100 ° C.
[10] The foaming agent component B) is converted into a subcritical state in the closed mold, and the closed mold is not a part of the mixing head of the mixing apparatus, and its internal volume and / or its internal pressure are externally introduced after the mixture is introduced. The method according to the above [8], which is designed so that it can be changed by action.
[11] A step of supplying a composition comprising the isocyanate-reactive compound A) and the surfactant C) according to [1],
A step of supplying a composition comprising the blowing agent B) present in the near-critical or supercritical state and the isocyanate D) present in the blowing agent B) according to the above [1];
-Mixing the two compositions;
-The step of reducing the pressure of the resulting composition mixture to convert the blowing agent into a gaseous state
A process for producing a polyurethane foam, comprising:
[12] A polyurethane foam obtained by the method described in [8] or [11] above.
[13] The polyurethane foam as described in [12] above as a foam having an average pore diameter of 10 nm to 10000 nm.
[14] The polyurethane foam according to the above [12], which has a pore density of 10 ⁷ pores / cm ³ to 10 ¹⁸ pores / cm ³ .
[15] Use of the reaction mixture according to the above [1] for producing a polyurethane foam.

Glossary
Desmodur® 44V20L: a mixture of diphenylmethane-4,4′-diisocyanate (MDI) with isomers and higher functional homologs having an isocyanate content of 31.4% by weight, Bayer MaterialScience AG
Desmodur® 44V70L: a mixture of diphenylmethane-4,4′-diisocyanate (MDI) with isomers and higher functional homologs having an isocyanate content of 30.9% by weight, Bayer MaterialScience AG
Desmodur® VP.PU 1806: Mixture of diphenylmethane-4,4′-diisocyanate (MDI) and diphenylmethane-2,4′-diisocyanate, Bayer MaterialScience AG
Desmodur® T 80:80:20 ratio of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate (TDI), Bayer MaterialScience AG
Desmophen® VP.PU 1431: Bifunctional polyester polyol, Bayer MaterialScience AG, hydroxyl number 310 mgKOH / g
DABCO: 1,4-diazabicyclo [2.2.2] octane DBTDL: dibutyltin dilaurate
Silwet® L-7607: Momentive siloxane polyalkylene oxide copolymer

  In order to determine the appropriate isocyanate, the solubility of various isocyanates in the blowing agent was tested.

  The solubility of monomeric MDI (Desmodur® VP.PU 1806), Desmodur® 44V70L and TDI (Desmodur® T 80) in propane, at a temperature of 25 ° C. and a pressure of 220 bar, etc. The volume was measured by premixing isocyanate and propane. VP.PU 1806 and Desmodur 44V70L formed two phases, which revealed that in each case about 20% propane was dissolved in the lower phase (isocyanate). On the other hand, Desmodur® T 80 was completely miscible with propane. That is, one phase was formed.

  The solubility of monomeric MDI (Desmodur® VP.PU 1806), Desmodur® 44V70L and TDI (Desmodur® T 80) in carbon dioxide at a temperature of 25 ° C. and a pressure of 220 bar, It was measured by premixing an equal volume of isocyanate and carbon dioxide. VP.PU 1806 forms two phases, about 50% carbon dioxide dissolves in lower phase (isocyanate), Desmodur 44V70L forms two phases, about 50% carbon dioxide dissolves in lower phase (isocyanate) It became clear. On the other hand, Desmodur® T 80 was completely miscible with carbon dioxide. That is, one phase was formed.

Determination of the critical point in the mixture with carbon dioxide To ensure that the blowing agent mixture is supercritical or near critical, Desmodur T 80 and hexamethylene diisocyanate were tested for critical parameters in the mixture with carbon dioxide. For HDI, the critical point at a temperature of 323 K was found to be when the molar fraction x _c = 0.94 and the pressure p _c = 165 bar. For Desmodur T 80, the critical point at a temperature of 323 K was when the molar fraction x _c = 0.90 and the pressure p _c = 159 bar.

  The microemulsion that can be obtained according to the previous teachings was converted into polyurethane foam. For this, a mixture of polyol, catalyst (DBTDL and DABCO) and surfactant was mixed with carbon dioxide at 34 ° C. and a pressure of 170 bar. Without being bound by any particular theory, it is believed that this process resulted in a microemulsion of supercritical carbon dioxide droplets in the polyol phase. This emulsion was mixed with polyisocyanate in a high pressure mixing head. The reaction mixture was then introduced into the mold at a specific counter pressure. In the examples of the present invention, the mold was supercritical for carbon dioxide. After introduction into the mold temperature controlled to 35 ° C and residence time, the pressure was reduced to atmospheric pressure. The residence time was optimized for each foam. The weights shown in the examples are parts by weight. The total injection weight was 120 g in each case.

FIG. 4 is an electron micrograph of the polyurethane foam obtained in Example 1 of the present invention. This indicates that the average pore size is much smaller than 500 nm.
FIG. 5 is an optical micrograph of the polyurethane foam obtained in Example 2 of the present invention. This indicates that the pore size is much smaller than 50 μm.
FIG. 6 is an optical micrograph of the polyurethane foam obtained in Example 3 of the present invention. This indicates that the pore size is much smaller than 80 μm.
FIG. 7 is an optical micrograph of the polyurethane foam obtained in Example 4 of the present invention. This indicates that the pore size is much smaller than 60 μm.
FIG. 8 is an optical micrograph of the polyurethane foam obtained in Comparative Example 5. This indicates that the pore size is much larger than 100 μm.

1 External Phase 2 Internal Phase 3 Polyol Molecule 4 Isocyanate Molecule 5 Surfactant Molecule 6 Phase Boundary

Claims (3)

The emulsion comprises a first phase and a second phase, in which the following ingredients are:
A) Selected from the group consisting of polyether polyols, polyester polyols, polycarbonate polyols, polyether ester polyols and polyacrylate polyols having a hydroxyl number of 100 mg KOH / g to 800 mg KOH / g and an average hydroxyl functionality of 2 or more. Isocyanate-reactive compounds,
B) a linear, branched or cyclic _C 1 -C ₅ alkanes, linear, blowing agent selected from branched or cyclic _C 1 -C ₅ fluoroalkanes and the group consisting of carbon dioxide,
C) alkoxylated alkanol, alkoxylated alkylphenol, alkoxylated fatty acid, fatty acid ester, polyalkyleneamine, alkyl sulfate, alkyl polyether, alkyl polyglucoside, phosphatidylinositol, fluorinated surfactant, siloxane group-containing surfactant and bis A surfactant selected from the group consisting of (2-ethyl-1-hexyl) sulfosuccinate;
D) An emulsion-like reaction mixture suitable for conversion to polyurethane comprising an isocyanate having an isocyanate functionality of 2 or more,
Isocyanate-reactive compound A) is present in the first phase of the emulsion and blowing agent B) is present in the second phase;
Foaming agent B) is present in a supercritical state,
Isocyanate D) is present in the second phase in a proportion of not less than 10% by weight relative to the total amount of isocyanate D) in the composition ;
Reaction mixture, characterized in that surfactant C) is present in a proportion of 3% to 30% by weight . A step of supplying an isocyanate-reactive compound A) , a blowing agent B) present in a supercritical state, a surfactant C) and an isocyanate D) having the meaning described in claim 1, and the pressure of the resulting composition The manufacturing method of a polyurethane foam including the process of lowering and converting a foaming agent into a gaseous state.   Use of the reaction mixture according to claim 1 for the production of polyurethane foams.

Images